Isostatic presses must withstand very high pressure, and very large forces arise with increasing press tool sizes. It has been found suitable to take up the arising forces in a frame, which axially directly supports the cylindrical pressure chamber and the pressure chamber closure (arranged movable toward and from the pressure chamber for allowing the insertion of a press tool carried by the closure) in a closed position indirectly bearing against the portion of the frame situated opposite the pressure chamber. It is conventional to dimension a hydraulic cylinder, adapted for displacing the closure to and from its working position, so that the hydraulic cylinder withstands the axial forces occurring when the press is pressurized. With the high axial press forces which have lately become applicable, e.g. 6000 tons, it has however been found practically unreasonable to dimension the hydraulic cylinder for withstanding such large loads and for being able to carry out its working stroke in a time suitable for its purpose.
It is further known to introduce a filler body between the closure when the latter joins up with the pressure chamber and the opposing part of the frame for locking the closure in its working position. See U.S. Pat. No. 3,867,077, for example. It is further known from U.S. Pat. Nos. 3,698,843 and 3,677,674 to arrange a locking block for the closure instead of such a filler body, this locking block being mounted on the side members of the frame. In comparison with the filler body, such locks have a considerably lower mass and therefore lower inertia forces occur during driving of the locks to and from the working position, although the blocks exercise an unfavourable force effect on the frame legs. In accordance with the accounted known art, there is further required a comparatively large space for the members which are to block the enclosure in a working position, and further space is required around the press itself to allow the locking members to be completely moved away so that the press tool and pressure chamber closure can pass through the frame in a line operation, which is required for economic reasons in the optimum utilization of the expensive isostatic press.
One object of the invention is therefore to provide a new isostatic press with the aid of which the mentioned drawbacks are circumvented or reduced in connection with retaining the closure while the press is pressurized, guidance of press tools through the press frame and the stresses on the press frame.